This invention relates to the provision of telephone services at a customer premises over a wideband service channel and, in particular, to a method and apparatus for maintaining access to telephone services during power outages at the customer""s premises on telephone sets connected to voice over digital subscriber loop (VoDSL) derived telephone lines.
In the art of telephony, until relatively recently twisted pair copper loops have been used to provide a physical connection for single directory number terminations on the Public Switched Telephone Network (PSTN). This type of service is known in the art as a Plain Old Telephone Service (POTS) connection and provides a termination to which at least one telephone set is connected.
Recently the telecommunications industry has experienced an increase in the utilisation of telecommunications services which requires more bandwidth for service delivery to customer""s premises. One way to deliver increased bandwidth to a customer is to install more local loops between the customer""s premises and a servicing central office. Another way is to install higher bandwidth connections, such as optical fibre. However, any solution involving the installation of new infrastructure typically proves to be very costly. Considering the downward pressure on service pricing due to increased competition in the telecommunications market, large capital investments in new infrastructure are generally not practical.
Solutions have been developed for providing increased bandwidth over existing subscriber loops. One successful solution is digital subscriber loop (DSL) service which provides good data transfer rates for customers located in proximity of a central office. Several DSL service protocols have been developed. They include asymmetric (ADSL); symmetric (SDSL), rate adaptive (RADSL) and very high speed (VDSL) which are collectively referred to as xe2x80x9cXDSLxe2x80x9d services. This technology permits the provision of wide frequency bandwidth which provides a second communications channel over the same twisted pair subscriber loop used for telephone service delivery. Various service applications have been developed and deployed using xDSL technology, of which Internet access is a prime example. xDSL devices installed at a customer location or on the customer premises are respectively referred to as Customer Located Equipment and Customer Premises Equipment (CLE/CPE)
There is an increasing interest in providing multiple telephone line terminations at a customer""s premises using xDSL services. This interest is fuelled by, for example, an expanding small business workforce requiring office equipment that uses the PSTN as an interconnection medium; an increase in home-based businesses; and a demand for multiple telephone lines for family use.
The provision and deployment of multiple POTS terminations at the customers premises has to date largely been accommodated by installing multiple local loops between the customer""s premises and a servicing central office. The deployment of VoDSL, in which multiple telephone line terminations are derived from the DSL channel, has now enabled multiple telephone lines using a single subscriber loop. However, VoDSL has a disadvantage because during power interruptions the DSL channel derived lines are lost. Consequently, telephones connected to those lines are disabled and offer no access to lifeline services during the power interruption.
In the event of power interruption at the customer""s premises, current implementations of VoDSL CLEs/CPEs do not provide a contingency solution for maintaining service on the VoDSL derived lines. Nonetheless, in a VoDSL service offering in which VoDSL derived telephone lines are provided, in the event of power interruption at the customer""s premises, the telephone set connected to the wire loop termination remains in service because it is provided with power from the central office. However, the VoDSL derived telephone lines become non-functional and cannot be used to place calls. Consequently, the only way the customer is able to place an emergency call is to find the active telephone set connected to the wire loop termination. This is obviously not a desirable situation.
It is known in the art to provide power to telephone equipment in event of power interruption. U.S. Pat. No. 4,381,427 which issued Apr. 26, 1983 to the Applicant describes a local loop system for providing voice and data communications which enables signalling between a customer""s telephone and the central office in the event of power interruption. The system is located at the central office and only provides a return path for a local loop in the event of power interruption. The system is not adapted to maintain access to lifeline services through telephone sets connected to VoDSL derived line terminations because it is not adapted to supply power to the VoDSL CLE/CPE.
U.S. Pat. No. 4,730,311 which issued Mar. 8, 1988 to Carse et al. describes a system in which a battery backup is provided at the customer""s premises. There are shortcomings in providing backup power in the event of power interruption at a customer""s premises using devices such as un-interruptible power supplies or battery backups. Providing batteries or uninterruptible power supplies significantly increases the cost of the deployed CLE/CPE. Backup power supplies can only operate only for a limited period of time before the batteries employed are exhausted. Furthermore, batteries employed in providing backup power also have a limited operational life, and must be serviced and periodically replaced.
No solution is currently known in which VoDSL equipment provides access to lifeline services from telephone sets connected to VoDSL derived telephone lines in the event of a power interruption to the transceiver. Therefore, there remains a need to provide a method and apparatus in which all telephone sets connected to VoDSL derived telephone lines are enabled to maintain access to lifeline services in the event of a power interruption at the customer""s premises.
It is an object of the invention to provide a method and apparatus which maintains access to lifeline services for telephone sets connected to line terminations derived from a wideband service channel in the event of a power interruption to a transceiver providing the services.
The invention therefore provides a transceiver adapted to maintain access to lifeline services over telephones sharing a physical link with a wire loop termination in the event of a power interruption to the transceiver. If operating power to the transceiver is interrupted, the transceiver is adapted to connect a plurality of telephone interfaces associated with the wideband derived line terminations to the wire loop termination, thereby providing power to the interfaces so that access to lifeline services through all telephone sets associated with the transceiver is maintained.
In accordance with the invention, the transceiver is provided with switchover circuitry. While provided with operating power from the customer""s premises, the switchover circuitry decouples the telephone interfaces associated with the wideband derived line terminations from the wire loop termination. In the event of a power interruption, the switchover circuitry couples the telephone interfaces associated with the wideband derived line terminations to the wire loop termination, thereby providing operating power to maintain access to lifeline services to all telephone sets associated with the transceiver.
The switchover circuitry preferably automatically transitions from a first state to a second state when operating power is supplied to the transceiver. In the first state, the switchover circuitry couples the telephone interfaces derived from the wideband derived telephone lines in parallel to the wire loop. This permits outbound calls to be placed from any one of the telephones. In the second state, the switchover circuitry couples the telephone interfaces to respective circuits associated with the wideband derived telephone lines so that normal, multi-line operation is restored.
The switchover circuitry may be, for example, one or more electromechanical relays or solid state relays.
The wideband channel may be, for example, a digital subscriber loop (DSL) service channel such as a voice over digital subscriber loop (VoDSL) service channel.